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Individual Tree Crown Segmentation of a Larch Plantation Using Airborne Laser Scanning Data Based on Region Growing and Canopy Morphology Features
摘要： The detection of individual trees in a larch plantation could improve the management efficiency and production prediction. This study introduced a two-stage individual tree crown (ITC) segmentation method for airborne light detection and ranging (LiDAR) point clouds, focusing on larch plantation forests with different stem densities. The two-stage segmentation method consists of the region growing and morphology segmentation, which combines advantages of the region growing characteristics and the detailed morphology structures of tree crowns. The framework comprises five steps: (1) determination of the initial dominant segments using a region growing algorithm, (2) identification of segments to be redefined based on the 2D hull convex area of each segment, (3) establishment and selection of profiles based on the tree structures, (4) determination of the number of trees using the correlation coefficient of residuals between Gaussian fitting and the tree canopy shape described in each profile, and (5) k-means segmentation to obtain the point cloud of a single tree. The accuracy was evaluated in terms of correct matching, recall, precision, and F-score in eight plots with different stem densities. Results showed that the proposed method significantly increased ITC detections compared with that of using only the region growing algorithm, where the correct matching rate increased from 73.5% to 86.1%, and the recall value increased from 0.78 to 0.89.
关键词： airborne laser scanning (ALS),individual tree crown (ITC) segmentation,light detection and ranging (LiDAR),region growing,canopy morphology,larch plantation
更新于2025-09-19 17:13:59
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Fluorinated solid additives enable high efficiency non-fullerene organic solar cells
摘要： The use of processing additives to optimize active layer morphology in organic solar cells (OSCs) is a simple and impactful way to improve photovoltaic performance. However, the retention of high boiling point liquid additives affects the stability and lifetime of OSCs, necessitating the development of volatilizable additives that can improve efficiency at no cost to long-term device stability. In this study, three novel volatilizable solid additives, INB-1F, INB-3F, INB-5F, with different degrees of fluorination are rationally designed, synthesized, and added into photovoltaic solutions to fabricate OSCs. These additives evaporate upon thermal annealing and exhibit higher volatility as the number of fluorine atoms increases. Our device studies show that these additives can enhance the efficiency of PBDB-T-2F:BTP-4F binary cells from 15.2% to 16.5%, and those of PBDB-T-2F:IT-4F from 12.1% to 13.4%. Molecular dynamic simulations reveal attractive interactions between these additives and the non-fullerene acceptor BTP-4F, leading to enhanced intermolecular π–π stacking among BTP-4Fs, which is a favorable morphology change that we attribute as the origin of the enhanced performance and long-term stability. Our work presents a novel strategy to design new solid additives to replace liquid additives.
关键词： fluorinated solid additives,morphology,power conversion efficiency
更新于2025-09-19 17:13:59
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[IEEE 2019 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Multi-pair dual-wavelength Nd:CALGO laser
摘要： The path opening is a ?lter that preserves bright regions in the image in which a path of a certain length L ?ts. A path is a (not necessarily straight) line de?ned by a speci?c adjacency relation. The most ef?cient implementation known scales as O(min(L, d, Q)N) with the length of the path, L, the maximum possible path length, d, the number of graylevels, Q, and the image size, N. An approximation exists (parsimonious path opening) that has an execution time independent of path length. This is achieved by preselecting paths, and applying 1D openings along these paths. However, the preselected paths can miss important structures, as described by its authors. Here, we propose a different approximation, in which we preselect paths using a grayvalue skeleton. The skeleton follows all ridges in the image, meaning that no important line structures will be missed. An H-minima transform simpli?es the image to reduce the number of branches in the skeleton. A graph-based version of the traditional path opening operates only on the pixels in the skeleton, yielding speedups up to one order of magnitude, depending on image size and ?lter parameters. The edges of the graph are weighted in order to minimize bias. Experiments show that the proposed algorithm scales linearly with image size, and that it is often slightly faster for longer paths than for shorter paths. The algorithm also yields the most accurate results— as compared with a number of path opening variants—when measuring length distributions.
关键词： mathematical image analysis,morphology,unbiased,line segment,Path opening,length distribution,granulometry
更新于2025-09-19 17:13:59
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Effects of Short‐Axis Alkoxy Substituents on Molecular Self‐Assembly and Photovoltaic Performance of Indacenodithiophene‐Based Acceptors
摘要： The effects of central alkoxy side chain length of a series of narrow bandgap small molecule acceptors (SMAs) on their physicochemical properties and on the photovoltaic performance of the SMA-based polymer solar cells (PSCs) are systematically investigated. It is found that the ordered aggregation of these SMAs in films is enhanced gradually with the increase of alkoxy chain length. The single-crystal structures of these SMAs further reveal that small changes in the side chain length can have a dramatic impact on molecular self-assembly. The short-circuit current density and power conversion efficiency values of the corresponding PSCs increase with the increase of the side chain length of the SMAs. The π–π coherence length of the SMAs in the active layers is increased with the increase of the side chain length, which could be the reason for the increase of the Jsc in the PSCs. The results indicate that small changes in side chain length can have a dramatic impact on the molecular self-assembly, morphology, and photovoltaic performance of the PSCs. The structure–performance relationship established in this study can provide important instructions for the side chain engineering and for the design of efficient SMAs materials.
关键词： polymer solar cells,side chain engineering,morphology,small molecule acceptors,molecular self-assembly
更新于2025-09-19 17:13:59
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SEM analysis of grid elements in mono-crystalline and poly-crystalline based solar cell
摘要： A Photovoltaic cell is an electrical gadget that changes over light legitimately into power by photovoltaic impact. Semiconductor materials are the fundamental materials they are made of. Cells are intended to deal with daylight and are made of single intersection or multijunction for different retention and charge partition instrument. Sun based cell con?guration includes determining the parameters of a solar cell structure to expand pro?ciency. Effectiveness of a sun-oriented cell basically relies upon Grid compo- nents (Ribbon, Busbar, Pad and Finger), Textures, materials and formats. Ray Tracing and Surface Morphology with different periodicity also in?uences the ef?ciency of Solar Cell due to change in Photo Current Densities. In this paper, SEM investigation and surface morphology are performed on lat- tice components of both mono and poly crystalline sunlight-based cells which legitimately impacts cell effectiveness.
关键词： Ribbon,Surface morphology,Busbar,Pad,Ray tracing,Finger
更新于2025-09-19 17:13:59
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Donor Derivative Incorporation: An Effective Strategy toward High Performance All‐Small‐Molecule Ternary Organic Solar Cells
摘要： Thick-film all-small-molecule (ASM) organic solar cells (OSCs) are preferred for large-scale fabrication with printing techniques due to the distinct advantages of monodispersion, easy purification, and negligible batch-to-batch variation. However, ASM OSCs are typically constrained by the morphology aspect to achieve high efficiency and maintain thick film simultaneously. Specifically, synchronously manipulating crystallinity, domain size, and phase segregation to a suitable level are extremely challenging. Herein, a derivative of benzodithiophene terthiophene rhodanine (BTR) (a successful small molecule donor for thick-film OSCs), namely, BTR-OH, is synthesized with similar chemical structure and absorption but less crystallinity relative to BTR, and is employed as a third component to construct BTR:BTR-OH:PC71BM ternary devices. The power conversion efficiency (PCE) of 10.14% and fill factor (FF) of 74.2% are successfully obtained in ≈300 nm OSC, which outperforms BTR:PC71BM (9.05% and 69.6%) and BTR-OH:PC71BM (8.00% and 65.3%) counterparts, and stands among the top values for thick-film ASM OSCs. The performance enhancement results from the enhanced absorption, suppressed bimolecular/trap–assisted recombination, improved charge extraction, optimized domain size, and suitable crystallinity. These findings demonstrate that the donor derivative featuring similar chemical structure but different crystallinity provides a promising third component guideline for high-performance ternary ASM OSCs.
关键词： small molecules,thick films,morphology,structural similarity,organic solar cells
更新于2025-09-19 17:13:59
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Effect of polymer donor aggregation on active layer morphology of amorphous polymer acceptor-based all-polymer solar cells
摘要： Most of polymer acceptors for all-polymer solar cells (all-PSCs) are semi-crystalline. Amorphous polymer acceptors containing B←N unit represent a new kind of acceptor materials and possess unique phase separation behaviours in all-PSCs. In this work, to study their phase separation morphology and all-PSC device performance, we select three polymer donors with identical polymer backbone but different side chains to blend with an amorphous polymer acceptor (rr-PBN). Among the three polymer donors, J91 exhibits the strongest aggregation tendency in solution and moderate crystallinity in thin film. The J91:rr-PBN blend shows the most optimal phase separation morphology and the best all-PSC device performance. In comparison, J51 shows the least aggregation tendency in solution and the highest crystallinity in thin film. The all-PSC device of J51:rr-PBN blend exhibits sub-optimal active layer morphology and poor photovoltaic performance. These results indicate that the aggregation tendency in solution of polymer donor is the dominant factor in the phase separation of semi-crystalline polymer donor/amorphous polymer acceptor blend in all-PSCs.
关键词： crystallinity,morphology,all-polymer solar cells,aggregation in solution,phase separation
更新于2025-09-19 17:13:59
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Predicting the fatigue life of an AlSi10Mg alloy manufactured via selective laser melting by using data from Computed Tomography
摘要： A modelling strategy is proposed to evaluate the influence of defect morphology on the fatigue limit of additively manufactured Al alloys by: (i) obtaining an x-ray micro-computed tomography (μ-CT) 3D image of the material, (ii) computing the Equivalent Inertia Ellipse of each individual pore, (iii) modelling the influence of the defect on the fatigue limit through the DSG approach and, (iv) 3D mapping the criticality of each individual defect. For this fatigue study, an AlSi10Mg alloy was manufactured by selective laser melting using sub-optimal deposition parameters in order to produce large lack-of-fusion defects. After a T6 heat treatment, tension-compression fatigue tests, with R = -1, were conducted on specimens oriented with their loading axis either parallel or normal to the Z-axis of the additive manufacturing equipment. Two samples were characterised before μ-CT testing in order to characterise the initial 3D defect population. Each sample was fatigued step by step in order to determine the fatigue limit. The fracture surface was then carefully observed using a scanning electron microscope (SEM) in order to identify the critical defect in the initial μ-CT image. A comparison with the fatigue results led to the following conclusions: (i) when the longest axis of the defect is perpendicular to the load axis, modelling the defect as an equivalent inertia prolate ellipse gives better results (5 % error on the fatigue limit) than modelling it as a simple equivalent sphere (22 % error on the fatigue limit), (ii) the prolate ellipse is not relevant when the longest axis of the defect is oriented along the loading axis; in this case an oblate equivalent ellipse should be used, (iii) the concept of ‘size’ for a complex 3D shaped defect should be linked to the inertia and the loading, (iv) with this approach, surface defects are shown to be more critical than internal ones for fatigue life and, (v) a 3D defect criticality map of the entire sample can be plotted to provide visual feedback on which defects are the most critical for fatigue life.
关键词： AlSi10Mg alloy,defect morphology,selective laser melting,fatigue life,Computed Tomography
更新于2025-09-19 17:13:59
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Construction of morphology-controlled nonmetal 2D/3D homojunction towards enhancing photocatalytic activity and mechanism insight
摘要： Highlights ? A novel nonmetal 2D/3D g-C3N4 homojunction was constructed via the facile surface in-situ polymerization process. ? The nonmetal 2D/3D g-C3N4 homojunction displayed the dramatically enhanced photocatalytic performance for degrading TC-HCl. ? The improved transfer and separation efficiency of charge carriers resulted from synergetic effect of 2D-3D structural coupling and energy band controlling. ? This work develops a feasible exemplificative strategy for fabricating new morphology-controlled at the interface between structural units owing to the matching chemical and electronic structures, nevertheless it still is difficult to fabricate the morphology-controlled nonmetal homojunction. Herein, a nonmetal 2D/3D homojunction is constructed via the facile surface Constructing homojunction is more favorable to transfer and separation of charge carriers nonmetal homojunctions to improve photocatalytic activity microspheres, mainly attributing to the improved transfer and separation efficiency of charge homojunction displays the dramatically enhanced photocatalytic performance for degrading tetracycline hydrochloride (TC-HCl) compared with single 2D CN nanosheets and 3D CC carriers resulted from synergetic effect of 2D-3D structural coupling and energy band controlling. Moreover, the important degradation pathway, intermediate products and surface of 2D g-C3N4 (2D CN) nanosheets. The obtained nonmetal 2D/3D CN/CC in-situ polymerization process, where 3D g-C3N4 (3D CC) microspheres tightly anchor on the photocatalytic mechanism are investigated in detail. This work develops a feasible exemplificative strategy for fabricating new morphology-controlled nonmetal homojunction to improve photocatalytic activity.
关键词： Degradation mechanism,TC-HCl,Nonmetal homojunction,g-C3N4,Morphology-controlled
更新于2025-09-19 17:13:59
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Evolving Crystal Morphology of Potassium Chloride Controlled by Optical Trapping
摘要： Dynamic morphology evolution of potassium chloride (KCl) crystal was demonstrated by surface optical trapping with a focused continuous-wave near-infrared laser. Optical trapping at an air/solution interface triggered the crystallization, and then the dynamic change in crystal morphology was observed in real time. We observed three different crystal morphologies of needle, rectangle, and cubic at the early stage of crystallization. As the laser power increases, the probability of generation of a cubic crystal increases, especially upon the irradiation with linear polarization. We also found laser-polarization-dependent morphology evolution by the continuous irradiation to the generated crystals. Upon linearly-polarized laser irradiation, the stepwise morphology evolutions from needle, rectangle, and eventually to cubic, which is an equilibrium shape of KCl crystal. While, circularly-polarized laser irradiation only induced morphology evolution from needle to rectangle, without morphology change into cubic, because the rectangle crystal was dissolved while crystal rotating. It was made possible to observe such a unique morphological evolution due to the spatiotemporal controllability of our crystallization method. The dynamics and mechanism of these intriguing phenomena are discussed from the perspective of a dense cluster domain formed by optical trapping before nucleation.
关键词： laser polarization,potassium chloride,crystal morphology,optical trapping,surface crystallization
更新于2025-09-19 17:13:59